The basic formula: your earnings history determines your benefit

Your SSDI payment is based on your Primary Insurance Amount (PIA), which Social Security calculates from your lifetime earnings record. The agency looks at your highest 35 years of earnings, adjusts them for inflation to current dollars, and then applies a formula that gives you a larger percentage of your early earnings and a smaller percentage of your later ones. This is why someone who earned $30,000 a year does not receive half what someone earning $60,000 receives—the formula is weighted to replace a higher percentage of lower incomes.

The exact dollar amount you receive each month depends on how old you were when you became disabled and what your earnings looked like before that point. If you became disabled at 35, Social Security uses your earnings from age 21 onward (or from when you started working, if later). If you became disabled at 55, it still uses your highest 35 years, which means some of your lowest-earning years may be included in the calculation.

You cannot see the exact formula Social Security uses—it changes slightly each year—but you can see your own earnings record and get an estimate of what your benefit would be. The Social Security website has a calculator that shows rough numbers based on your age and reported earnings.

Key Takeaways

  • Your SSDI payment comes from a formula based on your 35 highest-earning years, adjusted for inflation, not from a fixed percentage of your current or past salary.
  • The formula replaces a larger share of lower earnings and a smaller share of higher earnings, so two people with different salaries do not receive proportionally different benefits.
  • Your age at the time you became disabled affects which years count toward your benefit, because Social Security always uses your 35 highest years.
  • You can request a detailed earnings record from Social Security and use their online calculator to estimate your benefit amount before you file.
  • If you return to work, your benefit may be reduced or suspended depending on how much you earn, and this reduction follows specific rules that change based on your age and work history.

How Social Security adjusts your past earnings for inflation

Social Security does not use your actual dollar amounts from 1995 or 2005. Instead, it indexes your earnings—it multiplies them by a factor that brings them to current-year value. This means a $20,000 salary from 1990 might become $50,000 in today's dollars for calculation purposes. The indexing factor is based on national wage growth, not the consumer price index, so it reflects what wages have actually grown in the economy.

The indexing happens only for years before you turn 60 (or before you became disabled, if that was earlier). Years after that are counted at their actual dollar value. This is why your earnings in the year you became disabled matter more than earnings from 20 years earlier—they are not adjusted down.

You can see your indexed earnings on your Social Security Statement, which you can request online at ssa.gov or by calling 1-800-772-1213. The statement shows what Social Security recorded for each year and what it indexed those amounts to.

The bend points: why lower earners get a higher replacement rate

After Social Security indexes your earnings and selects your 35 highest years, it calculates your Average Indexed Monthly Earnings (AIME) by dividing the total by 420 months. Then it applies the bend point formula, which is the part that makes the system progressive.

The bend points are dollar thresholds that change every year. For 2024, they are different from 2023, and they will be different again in 2025. Social Security takes your AIME and applies a percentage to each bracket: you might receive 90% of the first $1,174, then 32% of earnings between $1,174 and $7,078, then 15% of anything above that. These percentages and thresholds are set by law and do not change, but the dollar amounts adjust annually based on wage growth.

This is why someone who earned $25,000 a year for 35 years receives a higher percentage of their pre-disability income than someone who earned $100,000 a year. The lower earner's entire AIME falls into the highest-percentage bracket, while the higher earner's AIME is spread across all three brackets, with most of it subject to the lower 15% rate.

What happens if you have gaps in your work history

If you did not work for several years—because you were in school, raising children, unemployed, or incarcerated—Social Security can drop up to five years of zero earnings from your calculation. This is called the dropout years provision. If you have more than five years of no earnings, the lowest-earning years are used instead.

This matters most for people who became disabled young. A 30-year-old who worked from age 22 to 28, then had no earnings from 28 onward, would have only 6 years of actual work history. Social Security would use those 6 years and drop 5 years of zeros, leaving 24 years of calculation based on zero earnings. The result is a much lower benefit than someone who worked steadily.

You cannot add years to your record retroactively, but you can check your earnings record to see whether Social Security recorded all the years you actually worked. If your employer did not report your earnings or reported them under the wrong name or Social Security number, you may be able to correct it with documentation like old tax returns or W-2 forms.

How work after you become disabled affects your payment

If you return to work while receiving SSDI, your benefit does not automatically stop, but it may be reduced or suspended depending on how much you earn. During the first nine months you work (called the Trial Work Period), you can earn any amount and keep your full SSDI payment. After that, if your earnings exceed the Substantial Gainful Activity (SGA) threshold—which is $1,550 per month in 2024 for non-blind individuals—your benefits will be suspended.

Once your benefits are suspended, you enter the Extended Period of may be able to access (EPE), which lasts 36 months. During this time, you can work and earn above the SGA threshold without losing benefits in any month you earn below SGA. After the EPE ends, if you are still working above SGA, your benefits stop entirely. However, you have a Medicaid continuation period that can last up to 93 months, so you keep health coverage even if cash benefits end.

The SGA threshold changes every year, and it is different for blind individuals. You should report any work to Social Security as soon as you start, because failing to report can result in overpayments that you will be asked to repay.

Why your benefit amount may differ from what you expected

Many people are surprised by their SSDI amount because they assume it is a percentage of their recent salary. It is not. It is based on a 35-year average, adjusted for inflation and run through a formula that weights lower earnings more heavily. Someone who earned $60,000 a year for the last five years but only $20,000 a year for the 30 years before that will receive a much lower benefit than someone who earned $60,000 consistently.

Your benefit also does not include any adjustment for the cost of living in your state or region. A $1,500 monthly SSDI payment is the same whether you live in rural Mississippi or San Francisco. Some states supplement SSDI with additional payments, but most do not.

If you believe Social Security made an error in calculating your benefit, you can request a detailed explanation of how they arrived at your amount. Call 1-800-772-1213 and ask for a benefit calculation statement. This document shows your indexed earnings, your AIME, and the bend point formula applied to your case. If you find an error in your earnings record, you can file a correction request, though you generally have only three years, three months, and 15 days from the end of the year the earnings were reported to correct them.

Frequently Asked Questions

Can I increase my SSDI payment by working more before I file?

Only if you have not yet reached the age when Social Security will calculate your benefit. If you are currently disabled and working, additional earnings will be indexed and may replace some of your lower-earning years, which could increase your benefit. However, if you are already receiving SSDI, working more will not change your payment amount—it may only trigger the work rules described above.

What if I worked in another country—does that count toward my benefit?

Social Security counts earnings from work in the United States only. If you worked abroad, those years do not appear on your U.S. earnings record. However, some countries have agreements with Social Security that allow credits earned there to count. You would need to contact Social Security directly to determine whether your foreign work history qualifies.

Does my SSDI payment increase when I turn 65?

No. Your SSDI payment converts to a retirement benefit at your full retirement age, but the amount stays the same. The conversion is administrative only—you do not reapply or recalculate. Your benefit was already based on your full lifetime earnings, so there is no increase at 65.

Why is my spouse's benefit based on my earnings record?

Family members can receive benefits on your SSDI record if they meet certain conditions: a spouse age 62 or older, a spouse of any age caring for your child under 16, or an unmarried child under 19 (or 22 if in school). Their benefit is calculated as a percentage of your PIA, not as a separate calculation. The total family benefit is capped at 150% to 180% of your own benefit, depending on how many family members are receiving.

Can I see the exact bend points used to calculate my benefit?

Yes. Social Security publishes the bend points for each year on their website. You can also see them on your benefit calculation statement, which shows the exact percentages and thresholds applied to your AIME. The statement is the most reliable source because it shows what was actually used in your case.